At over 250 acres, Eagle Bike Park is one of the largest around. Located in the town of Eagle, Idaho, a suburb of Boise, the park is packed with technical features and regular trails, the most prominent of which is the Stormin' Mormon freeride line, measuring in at 8/10 of a mile long with about 30 table top jumps and three drops.
Other bike park features include three freeride jump lines ranging from beginner to expert, a pump track, beginner and intermediate dirt jumps, dual slalom race course, mountain cross race course, a skills park with three lines of wooden features (again, ranging from beginner to expert) a downhill race course, a BMX track, short track cross country race course, cyclocross race course, and seven miles of cross country trails. Those XC trails also connect to other singletrack trails in the area, as well as the local bike paths, to provide excellent connectivity between all biking opportunities in Eagle.
See Google Maps location.
http://www.singletracks.com/item.php?c=1&i=7047